A known shielding device of this kind is disclosed in U.S. Pat. No. 4,444,465 and consists of an undeformable U-shaped shaft section of flanged plastic plate material. The shaft section is placed upside down over the housing of the screen, i.e. with the legs of the shaft section pointing downwards. Thus, the body of the shaft section rests on the upper side of the housing, while its legs are on either side of the screen. In the extended position, the shaft section projects from the housing beyond the displaying screen and prevents irritating reflections of natural light and/or artificial light on the glass of the screen, thereby rendering the image shown on the displaying screen clearer. The known shielding device is collapsible by pushing it over the housing into a position in which the shielding device does not project beyond the screen.
This known shielding device has several disadvantages. In order to ensure that the shielding device remains balanced in its operating position, a special fastening device is required which consists of a bracket which has to be attached on top of the housing. As a result thereof, a relatively expensive part is required which greatly affects the outward appearance of the housing. Furthermore, the shielding device is bulky under any circumstance, which can be irritating and may also adversely affect the outward appearance of the housing of the screen. In addition, the user is required to sit straight in front of the displaying screen when the shielding device is extended, as the shielding device is too much of a nuisance when viewing the displaying screen at an angle.